I'm a huge fan of SCT tuning but any noticable performance with cost $

Best bang for the buck is cams.
https://dodgeforum.com/forum/3rd-gen...formation.html

Boost will land you an easy 300 rwhp.
https://dodgeforum.com/forum/3rd-gen...cessories.html

HHR and other efans.
https://dodgeforum.com/forum/3rd-gen...installed.html

For NA engines look at 4.10 gears. For boosted applications, 3.55 to 3.92 gears.

Good luck.